The present invention relates to an X-ray diagnostic apparatus.
In an X-ray diagnostic apparatus, halation of a fluoroscopic and/or photographic image is a phenomenon caused by an image forming device (camera tube) when luminous energy (a quantity of light) increases in a region at which the X ray absorption rate is extremely small in the vicinity of an area to be observed, in spite of the fact that the luminance (brightness) of an object to be observed is appropriately adjusted. To prevent this halation, conventionally, a method of using compensation filters (containing an X-ray absorbing substance) has been so far adopted. In this method, the compensation filters are previously prepared on the basis of some standard halation patterns. In more detail, the compensation filters are formed on the basis of a plurality of standard patterns according to the site to be diagnosed. When having recognized the presence of a halation in a monitor image, the operator inserts an appropriate compensation filter into an illumination field at the front of an X-ray tube by manipulating a compensation filter control device. In this case, the operator controls the location of the compensation filter by watching the halation in the monitor image and the compensation filter inserted into the Illumination field, In such a way that the halation can be eliminated most effectively and thereby the image can be observed most clearly. In this halation prevention method, since a dose of the X-rays radiated upon an object to be diagnosed is reduced at only the region where the compensation filter is inserted, as compared with the other region, the dose of the X-rays incident upon the camera tube can be reduced at the halation portion.
In the above-mentioned conventional method, however, since the previously determined pattern of the compensation filter does not necessarily match the shape of the actual halation, there exists a problem in that it is impossible to eliminate halation perfectly. Further, since the compensation filter formed of an X-ray absorbing substance is additionally inserted into the image, the compensation filter is also displayed as an image, thus resulting in shortcomings such that there exists a possibility of erroneous diagnosis because the operator mistakes a shadow of the compensation filter for a shadow of an object to be diagnosed. Further, whenever halation occurs, since the operator must insert the compensation filter and further adjust the location of the compensation filter, there exists another problem in that the diagnosis operation is complicated and therefore it takes a long time for the diagnosis.